Environmental health is the branch of public health that focuses on the interrelationships between people and their environment, as well as how to foster healthy and safe communities. It addresses the societal and environmental factors that increase the likelihood of exposure and disease. Poor environmental quality has its greatest impact on people whose health status is already at risk. Environmental threats to health frequently require rapid and urgent action to protect the environment for both present and future generations. This chapter describes key concepts in environmental health and related risks.”